ESTRO 2023 - Abstract Book

S1277

Digital Posters

ESTRO 2023

Data is analyzed using the Wilcoxon test and Cox regression. The Shapiro-Wilk test is used to study normality. We consider a significant result if p-value < 0.05. Forty-seven patients, representing a total of 51 metastatic lesions were selected (Table 1). The median follow-up period was 90 months from diagnosis (interquartile range, IQR, 74) and 15 months from SBRT (IQR 29). It was delivered between 1 to 3 fractions with a dose between 12 to 30Gy. Results The main location where SBRT was performed was bone (n = 33) followed by adenopathy (n = 18). Regarding the dose, the most used was the scheme of 18Gy in a single fraction (n = 16) followed by 30Gy in 3 fractions (n = 13). Two patients (4.3%) developed local progression with a median of 5.50 months. Distant progression occurred in 9 patients (20.5%) with a median of 4 months. 71.4% of lesions presented a radiological response after SBRT. 2 deaths occurred, and none of them were related to prostate cancer. An increased risk of disease progression after SBRT was found in patients who developed castration-resistant prostate cancer (CRPC): HR 16.44, CI95% [3.48; 77.67]; p-value < 0.001. Ten patients (22.7%) developed biochemical progression after SBRT, with a median of 4 months. Two deaths occurred during the follow up period, neither of which was related to prostate cancer. A significant drop in the PSA value after 6 months of treatment was identified (2.20ng/ml vs 0.25ng/ml, p-value 0.014) (Figure 1). Eight patients presented acute toxicity (mild pain in all cases). Four patients (9%) developed chronic toxicity: 3 mild pain and 1 rectovesical fistula. Any patient presented a grade 4 toxicity neither needed to stop the treatment.